Howdy perpetual arguers!

Here is the good one for you on eHam.net

http://www.eham.net/articles/6512

between yours truly (right) and Tom, W8JI (wrong).

It centers around the argument that the RF current in the antenna loading coils
is (or not) equal. Classic case of "theory" (wrongly applied) to real life
measurements and facts. There is referenced previous article that started it
all and on my budding web site www.K3BU.us full text with pictures at
http://www.k3bu.us/loadingcoils.htm

It looks like this factor is not properly accommodated in modeling programs
using loading inductors in antenna elements. In view of the above, time
permitting, I will try to do some work and try to shed some more light on the
subject.

Any experiences out there, rather than more "reasons" why it ain't so?
Proper accommodation in modeling programs can give substantial improvement in
loaded elements modeling.

Let the games begin :-)

Yuri, K3BU

On 29 Oct 2003 18:58:40 GMT, oSaddam (Yuri Blanarovich)
set up a tar baby:


|
|Let the games begin :-)

You say (at least I think you said): "Roy Lewallen, W7EL, author of
EZNEC and Wes Stewart, N7WS recommend workarounds to replace the coil
with cylinder of similar size or breaking the coil to number of
physical segments with appropriate inductances."

I'll admit to forgetting more things as I get older but I'll be damned
if I remember making any such statement.

Can you post a link to this so I know what it is that you think I
said, or what I said that I don't remember saying?

Wes Stewart N7WS

Can you post a link to this so I know what it is that you think I
said, or what I said that I don't remember saying?

Wes Stewart N7WS



Without going the route of providing "evidence" I posted the question about the
modeling loading coils here, and Roy and you provided suggestions of the
described workaround (if my memory doesn't fail me :-)

Yuri

On 29 Oct 2003 20:40:11 GMT, oSaddam (Yuri Blanarovich)
wrote:

|
|Can you post a link to this so I know what it is that you think I
|said, or what I said that I don't remember saying?
|
|Wes Stewart N7WS
|
|
|
|Without going the route of providing "evidence" I posted the question about the
|modeling loading coils here, and Roy and you provided suggestions of the
|described workaround (if my memory doesn't fail me :-)

In other words, I didn't say it.

|
|Yuri

Can you post a link to this so I know what it is that you think I
said, or what I said that I don't remember saying?

Wes Stewart N7WS


You are right. It wasn't you, it was and credit belongs to Richard Clark,
KB7QHC.
I apologize for the error, which was caused by my confusion between two of you
7's.
Now that you made posting on eHam.net I went back to the archives and found the
posting and its rightful author.
Sorry if it caused any problems and made you to jump to conclusion that I am
making things up. I will be more careful with references.

Yuri, K3BU.us

On 03 Nov 2003 15:46:01 GMT, oSaddam (Yuri Blanarovich)
wrote:

|
|Can you post a link to this so I know what it is that you think I
|said, or what I said that I don't remember saying?
|
|Wes Stewart N7WS
|
|
|You are right. It wasn't you, it was and credit belongs to Richard Clark,
|KB7QHC.
|I apologize for the error, which was caused by my confusion between two of you
|7's.
|Now that you made posting on eHam.net I went back to the archives and found the
|posting and its rightful author.

Why did it take my posting on eHam to get you do do this? The quote
above was directed to you in this forum days ago.


|Sorry if it caused any problems and made you to jump to conclusion that I am
|making things up. I will be more careful with references.

Okay. Thanks.

N7WS:

Why did it take my posting on eHam to get you do do this? The quote
above was directed to you in this forum days ago.


I thought it was you, didn't make much of it. If it was so important and you
accused me of making things up, implying that article was misleading, I
investigated Google search options and found the proper posting by KB7QHC and
posted the correction. Ju's human me, sorry.

Yuri

On 03 Nov 2003 15:46:01 GMT, oSaddam (Yuri Blanarovich)
wrote:

You are right. It wasn't you, it was and credit belongs to Richard Clark,
KB7QHC.

Hi Yuri,

The observation was hardly original and I thought it answered the same
question that launched this current thread (in other words, your
complaint of the shortfall of modeling was already acknowledged with a
work-around offered).

What I do not see is any follow-through for that same suggestion. The
complaint has been offered twice, but the resolution abandoned as
though it had never been made.

I've visited your page, and in an effort to wean out the details (you
don't go to much effort to offer an unadorned, plain, vanilla
specification for the radiator). I had to guess about the coil length
(judging from its only metric being 2.5" diameter) and inductance (you
dismiss the importance of its Q and wholly leave this metric blank).
Tom cites a 300µH inductor, but if we are to believe he's unreliable,
then why are there no better sources of this fundamental information?
Using that same metric (coil diameter) I guess the vertical element
was 3/8" (but one picture clearly shows a thin whip which makes
charges of mismodeling a sure prospect regardless of honest effort).
60 radials are suggested, but no mention of length (if my attempts to
model it yield answers that don't fit your numbers - is it my fault?).

So I proceed with any number of presumptions and with every prospect
of charges of cooking results - this is the same odds offered in
prospecting eh/cfa claims.

OK, the plain vanilla radiator 93" tall (3/8" stock) in 93 segments
surrounded by 60 X 93" radials (#12 wire) ALL elevated 6" above a
real, medium ground.
SRC DATA @ 7.1MHz = 0.7995 - J 810.9 ohms
Current varies from 1A at drive point to 0 at tip

The adornment consists of this underspecified coil being decimated and
spread across 10 inches of space in the middle of the radiator with
lumped values of 30µH each. For the life of me, I don't know what
this exercise was to prove given the results:
SRC DATA @ 7.1MHz = 1.258 - J 1561 ohms
Current varies from 1A at the drive point to 0 at the tip
One variation on the first pass design is that when this current hits
the decimated inductor, the current drops to 0 a few inches before the
first inductor section and quickly develops an 180° shift over those
next few inches which persists on out to the tip. At the bottom of
the coil sections, the current again picks up to roughly 100mA
climbing to roughly 150mA at the top and then declining over the
remaining length of radiator. It would seem that anyone could craft
any assortment of conditions to support any of a dozen new theories
from this kind of legerdemain.

As far as I am concerned, these are merely a list of facts based upon
a poor specification supporting an argument that suffers from an
indistinct agenda apart from its lengthy round of 't'ain't so-isms.
Yuri, I still see no effort from you to fill in the current
distribution readings apart from a rather thin data-set of the two
points offered. Your call of warning was already answered some time
ago. Does the current vary across the inductor by this offered
method: yes! and in spades. Does it vary as you describe it? No, but
simple heat can explain that.

73's
Richard Clark, KB7QHC

Richard KB7QHC writes:

I've visited your page, and in an effort to wean out the details (you
don't go to much effort to offer an unadorned, plain, vanilla
specification for the radiator). I had to guess about the coil length
(judging from its only metric being 2.5" diameter) and inductance (you
dismiss the importance of its Q and wholly leave this metric blank).

Our major disagreement with W8JI was is the current accros antenna loading the
same or is it appreciably different. I was just trying to argue that it is
signifficantly different, W9UCW has done multitude of tests and measurements
and supported my position. I had practical experience of knowing that bottom of
uniform coils get hotter than middle or top, I fried heatshrink tubing at the
bottom of the coils and this was good enough for my practical knowledge that
current must by higher at the bottom. ON4UN book also supports that.

The second step in our quest of properly mastering the phenomena is to
investigate the relationships, magnitudes and have it properly accounted for in
the modeling software. W9UCW provided some info, data and pictures, he has lot
more and is willing to cooperate further, be it writing concise article (he is
preparing material for the book also) or answer questions or provide more info.
I told him about this NG, so he might show up. So if we are ready to bridge the
idea that current is different and implement that in the software, lets roll.
So far it appears that Roy still has a problem with understanding what is going
on.

Yuri

On 03 Nov 2003 21:43:22 GMT, oSaddam (Yuri Blanarovich)
wrote:

So if we are ready to bridge the
idea that current is different and implement that in the software, lets roll.
So far it appears that Roy still has a problem with understanding what is going
on.

Yuri

Hi Yuri,

That, in fact, is not so. The problem as expressed by you was
acknowledged and a solution offered BEFORE you started this thread.
There was a protocol given THEN to obtain a correct perspective to the
issue.

Do you propose to offer additional data showing the current
distribution over the entire radiator, or are we going to be indulged
in retread arguments that have been answered?

73's
Richard Clark, KB7QHC